In previous analyses [1]} and [2]}, the rigidity dependence of the diffusion coefficient was modeled as a single power law in rigidity so that \(D(R) \propto R^{-\delta _\mathrm {esc}}\)  and \(\tau _\mathrm {esc} \propto R^{\delta _\mathrm {esc}}\) . This is a good approximation for CRs that are in the diffusive regime for all the relevant rigidities. For a more realistic treatment we use a fit to the diffusion simulation of [3]} with the functional form suggested in [4]} leading to numerically very similar results as found in [4]}:
